 Mitral Valve Repair or Replacement on the Beating Heart
(#2000-1899 ... June 8, 2000)
Borut Gersak, MD, PhD
Department of Cardiovascular Surgery, University Medical Center, Ljubljana, Slovenia
ABSTRACT
Background: Beating heart (off-pump) coronary artery bypass grafting (CABG) techniques have led us to consider the possibility of performing mitral valve repairs and replacements (with or without CABG) on the beating heart.
Methods: If CABG had to be performed in addition to the valve procedure, CABG was done first on the beating heart without cardiopulmonary bypass, if possible. For the valve procedure, the aorta was cross-clamped and the beating-heart status was maintained throughout the whole procedure with continuous, warm, oxygenated blood coronary-sinus perfusion.
Results: We used this technique in 23 patients with extremely low ejection fractions, 78% of whom were in New York Heart Association (NYHA) class 4 and 17% of whom were in New York Heart Association (NYHA) class 3. The procedures were: mitral-tricuspid (11 patients), mitral-aortic (7 patients), mitral-tricuspid CABG (1 patient), and mitral-aortic CABG (4 patients). The total early mortality was 13% (3 of 23 patients). Two were in-hospital deaths. One patient with triple-vessel disease and acute mitral insufficiency (AMI) on intra aortic ballon pump had been operated on six days after AMI. The cause of death was systemic meticillin resistant staphyloccocus aureus infection. (Eight days prior to our operation, arthrodesis of the talocrural joint was performed by an orthopedic surgeon.) The other death was a female patient who was operated on after previous multiple cerebrovascular infarctions (CVIs) (cause of the death was CVI). In addition, one patient died one month after the operation because of prosthetic valve endocarditis on aortic and mitral valves (silver-coated silzone aortic and mitral valves were implanted because of chronic latent asymptomatic tibial osteitis). None of these deaths were cardiac related.
Conclusions: The main advantages of beating heart surgery are: 1) the perfused myocardial muscle, 2) the heart not doing any work, 3) no reperfusion injury, 4) the possibility for ablation of atrial fibrillation on the beating heart, and 5) testing of the mitral valve repair is done in real physiologic conditions in the state of left ventricle beating tonus. The procedure could be the procedure of choice for the valve operation or combined operations in high-risk patients with low ejection fractions.
INTRODUCTION
Retrograde blood cardioplegia was successfully introduced [Buckberg 1990] to protect the cardiac muscle, especially during cardiac arrest, and has been used recently in cardiac surgery [Kawasuji 1997]. Also, minimally invasive direct coronary artery bypass (MIDCAB) and off-pump coronary artery bypass (OPCAB) operations on the beating heart have been performed recently [Tasdemir 1998]. With these successful cardiac procedures in mind, we were led to the premise that with retrograde oxygenated blood perfusion, it would be possible to perform operations on the beating heart, even in open heart surgery such as aortic or mitral valve surgery. Everyone would agree that the most damaging effect of the cardioplegia is reperfusion injury [Allen 1986]. It was obvious to us that retrograde continuous oxygenated blood perfusion would cancel this effect.
The tricuspid valve repair (PTV) is normally performed on the beating heart, and it is from an operation like PTV that we may realize what problems or technical difficulties may arise during a mitral valve procedure; the walls of the ventricles are not flattened and the exposure of the mitral valve is challenging task. Also, the free walls of the ventricles with the interventricular septum are in a state of the tonus, so every force applied to better expose the aortic or mitral valve would be unsuccessful.
MATERIALS AND METHODS
Operation
Total cardiopulmonary bypass (CPB) is used to obtain the empty right atrium (RA). The RA is dissected as much as possible from the left atrium (LA) between the interatrial sulcus. An incision is made 1 cm from and parallel to the atrioventricular sulcus, opening the RA and exposing the coronary sinus (CS) opening. From outside the RA, the 4/0 polypropilene purse suture is made around the CS ostium and a retrograde cannula is inserted, a tourniquet is applied, and a catheter is connected with the retrograde oxygenated blood perfusion line.
Both vents (aortic and left ventricular) maximally drain the heart while, simultaneously, the aorta is clamped and the retrograde CS perfusion is started at a rate of approximately 300 mL/min, giving a retrograde mean pressure of 50 to 60 mm Hg [Eke 1997].
The incision parallel to the interatrial septum is made in the LA, exposing the LA and providing good visualization of the interatrial septum from both sides. The vertical cut, starting from the middle of the RA is made to the septum, toward and through the fossa ovalis, similar to that proposed earlier [Brawley 1980]. However, our incision is made in the direction of 45 degrees toward the CS, preserving the CS and the retrograde perfusion, and giving the typical H–V appearance. Hooks are then easily applied giving excellent exposure of the mitral valve. The procedure on the mitral valve is then performed and, if the mitral valve repair is made, the testing on the beating heart is done. The left ventricle is filled with saline, the aortic pressure is registered through the aortic vent, and the necessary corrections for the mitral valve are finalized. The aortic vent is then opened, the heart is emptied in full, and the vent is inserted in the left ventricle through the mitral valve or, if necessary, through the apex. At this point, if the mitral valve replacement was performed, the aortic valve replacement will be done next. The excision of the left auricle is performed with two layered 4/0 continuous sutures if the LA is enlarged or if the patient is in atrial fibrillation (AF). A continuous 3/0 polypropilene suture, starting at the fossa ovalis, is used to close the interatrial septum. The left atrium is sutured from the cranial portion toward the end of the atrial cut, reducing the LA. Next the RA is closed and, if the patient is in AF, the right auricle is removed, closing with two layered 4/0 continuous sutures.
Patients
At the time of introducing the technique of beating-heart valve procedures, we performed this operation on patients with extremely low ejection fractions and high NYHA class. Their characteristics are shown in Table 1 and Figure 1 [see Figure 1 :140:, Table 1 :142:]. The mean age of the patients was 60.39 years.
RESULTS
Table 2 shows the operative data for the valve procedures on the beating heart [see Table 2 :143:]; the types of procedures are shown in Figure 2 [see Figure 2 :141:].
The mean time of CPB was 100.34 minutes; mean aortic cross-clamp time was 67.39 minutes; mean creatine kinase (CK) on day 1 was 11.33; mean CK–MB (MB fraction of CK) on day 1 was 0.06; and mean flow through the coronary sinus was 414 mL/minute or 28.429 liters for the whole procedure.
Of the 23 patients who were operated on, 3 patients died. Two were in-hospital deaths. One patient (patient No. 12) with triple-vessel disease and acute mitral insufficiency on intra aortic baloon pump had been operated on six days after acute myocardial infarction. The cause of the death was systemic meticillin resistant staphylococcus aureus infection. (Eight days prior to our operation, arthrodesis of the talocrural joint was performed by an orthopedic surgeon.) The other death was a female patient (patient No. 11) who was operated on after previous multiple cerebrovascular infarctions (CVIs) (cause of the death was CVI. In addition, one patient (patient No. 5) died one month after the operation because of prosthetic valve endocarditis on aortic and mitral valve (silver-coated silzone aortic and mitral valves were implanted because of chronic latent asymptomatic tibial osteitis). None of these deaths were cardiac related.
DISCUSSION
Beating-heart surgery with CPB is not a novelty; it is being used routinely in repairing atrial septum defects, in pulmonary artery procedures, and as a method for tricuspid-valve repair.The tendency toward beating-heart surgery is shown in the first of experimental emergent surgeries: in repairing post-infarction ventricular septal defect with myocardial infarction exclusion; in the use of the endocardial patch on the beating heart with normothermic CPB; and in infusion of the ultra-short beta blocker [Takahashi 1996]. If so the heart muscle, which is already so affected, cannot stand any additional ischemic deficiency.
With these procedures, CPB also ensures a pumping function of the heart, compensating for the fact that the heart or great vessel cavity must be opened. With some procedures blood may reach the coronary arteries in a natural way. Operations such as valve replacements (aortic, mitral) have been performed on a beating heart using CPB to ensure circulation with oxygenated blood by attaching catheters directly to the ostia of the coronary arteries. Because of the many disadvantages of this technique (e.g., danger of damaged ostia, blocking the view in aortic valve replacement), we introduced the technically simpler procedure of supplying oxygenated blood retrograde through the venous system of the coronary sinus. Initiating retrograde cardioplegia, where the fluid is injected through the coronary sinus, flows through the venous system, capillaries, and then out the arterial end, requires a leap in traditional surgical thinking. Experimental studies have shown that most of the fluid escapes through the venous system (Tebez's veins) into the right atrium. Retrograde blood cardioplegia, related to antegrade blood cardioplegia, is today a method of achieving an arrested heart during heart surgery.
Just a step away from oxygenated blood flowing retrograde through the coronary sinus is retrograde cardiac perfusion. Some similarities exist between retrograde cardioplegia and retrograde cardiac perfusion (the insertion technique is the same, as is the physiologic principle), but there are two essential differences. In retrograde cardioplegia, the fluid that flows through the system is a crystalloid solution, mixed with cold or warm blood; in retrograde cardiac perfusion the fluid is warm (37°C), oxygenated blood, the same as blood that flows from the CPB to the aorta and throughout the body.
The basic requirements are:
1. Surgery on a beating heart using retrograde cardiac perfusion must be performed in normothermia (35°C to 37°C).
2. The catheter in the coronary sinus must be in place throughout the entire procedure and, under all conditions, must remain in place because it provides the heart with the blood it needs.
3. The blood in the retrograde perfusion system must maintain a temperature of 37°C. At this temperature we ensure maximal vasodilatation of cardiac veins, steady retrograde distribution and blood flow, and normal pressures in the venous system, which should not exceed 60 to 80 mm Hg of mean pressure. Optimal pressure is achieved by the CPB technician regulating the degree of blood flow through the coronary sinus.
4. Throughout the procedure, the heart volume and pressure must be unburdened.
Retrograde cardioplegia through the coronary sinus is today routine. It is generally accepted that the coronary sinus (vein system) can safely accept pressures between 50 and 60 mm Hg [Eke 1997]. The values have been observed experimentally on a beating heart, which functioned with ligature of the coronary sinus and blood flow to both coronary arteries and veins.
In experiments on an unburdened and still heart (which does not function) with pressures between 40 to 120 mm Hg in the coronary sinus, presence of extravascular bleeding on serial slices of the right and left ventricle has not been noticed. Under microscopic analysis, the slices have shown a normal presence and preservation of the structure of the heart [Gill 1997]. These studies show that the coronary sinus can withstand a somewhat higher pressure quite well during retrograde cardioplegia and hence during retrograde heart perfusion as well.
We can see in the myocardium in cardiosclerosis, as well as during experimental ischemia and hypoxia, that there exists a paradox: the inflow diminishes while the backflow increases. In reality, the expansion of the venous channel compensates for the deficiency of arterial vascularization of the blood supply, bringing nutritients to the myocardium by retrograde blood flow [Djavakhshvili 1997]. With age, the capillary net of the myocardium becomes sparse and sinusoids become wider and more prominent. The venous system of myocardium begins in the sinusoids, which contain endothelium as well as basal membrane in their walls.
Our technique of beating heart cardiac surgery on valves involves the constant retrograde coronary sinus perfusion of pure, normothermic, oxygenated blood. By giving the oxygenated blood retrograde, via coronary sinus, we are in fact giving the blood to the most important reservoir of the damaged myocardium. However, this is not the only advantage of beating-heart surgery. The three-dimensional architecture of the beating heart gives a direct opportunity to examine the mitral valve under physiologic conditions before, during and after completion of the repair. The commonly employed techniques permit inspection of the valve in a flaccid, arrested state that may not accurately reflect its function in the contractile heart.
Near-red spectrum spectroscopy is a useful method for constant determination of myocardial oxygenation during "warm" heart surgery. Studies made during perfusion with warm blood cardioplegia have shown that episodes of ischemia longer than 10 minutes have a consequence of less than optimal myocardial preservation (protection) and are to be avoided [Kawasuji 1997]. Encouraging results of myocardial preparation to ischemia (preconditioning) in experimental models of myocardial infarction or models with extended ischemia have revealed questions about the use of similar techniques as a support to conventional cardioplegia. Unfortunately, the connection between the combination of ischemic preconditioning and myocardial protection with "cold" blood cardioplegia, compared with using exclusively cold blood cardioplegia, did not show any better results [Cremer 1997]. Actually, it seems that this combination lowered the contractile capacity of the heart fibers.
It is important to emphasise that our early mortality was 3 of 23 patients (13%) and that none of the deaths were cardiac related. This is a good result, considering the preoperative data of the patients. It is clear that 78% were NYHA class 4, and 17% were NYHA class 3, totalling 95% in the high-risk group.
In the beginning we thought that only simple valve procedures were possible with this technique; however, we soon realized that this was not the case. Now we believe that this technique also enables complex mitral valve reconstruction, even such techniques as resection of the leaflets and aortic root enlargements. This is of special value because we strongly believe that it is advantageous to repair the valves of high-risk patients, thus leading to better long-term results.
It has been shown that current techniques of cardioplegia are not necessarily connected to avoiding ischemic myocardial damage in patients with high risk, such as a left ventricular ejection fraction of 0.25, arising myocardial infarction, developing and progressive myocardial ischemia, and elderliness [Perrault 1997], especially for those who are also scheduled for coronary artery bypass graft (CABG) surgery. We have two alternatives -- proceeding on a beating heart without CPB or proceeding on a beating heart using CPB.
Working on a beating heart using CPB has been found to be a better alternative, compared with the classic technique (still-heart CPB). Of course this alterative adopts the weaknesses of CPB, but eliminates the consequences of global myocardial ischemia.
If we have patients who require valve procedures in connection with the CABG, it is our strategy that the OPCAB technique is used (as in patients 1, 3, 5, 12, 15, which was 20% of our cases). If we have, as an additional procedure, mitral valve repair or replacement, we can still do the proximal anastomoses prior to this procedure. In the case of surgery on the aortic valve, the valve procedure is done first and, at the end, proximal anastomoses are sutured in the aorta.
MIDCAB and OPCAB techniques are still associated with acute regional ischemia in normothermic conditions at the time when the surgeon is suturing the distal anastomosis, which dictates a need for protecting the myocardial muscle under these conditions. One of the possibilities is to establish blood flowing through the coronary artery using an intraluminal shunt [Heijmen 1998], using pharmacological agents, or mechanically unburdening the ischemic heart during and after regional ischemia. With our technique of continuous coronary sinus perfusion during valve surgery in combination with CABG, we can perfuse the heart during the time of proximal anastomoses suturing.
The methods of protecting the heart muscle during intentional cardiac arrest and using CPB have approached simplicity and efficiency in the last forty years. Today cardioplegia is given antegrade and retrograde; blood cardioplegia is in use, either cold, moderate or warm. In the future we can expect efforts in initiating successful cardio-protective effects during cardiac preconditioning [Pirc 1995], preventing the destructive effects of accumulating calcium with inhibition of the sodium pump and the role of hydrogen ions in preserving the functions of the endothelium [Gersak 1996].
Coronary surgery without the use of cardioplegia or CPB, even in the presence of coronary artery disease and corresponding CABG, can present the ultimate form of protecting the heart muscle.
AUTHOR/ARTICLE INFORMATION
Presented at the Third Annual Meeting of the International Society for Minimally Invasive Cardiac Surgery, Atlanta,Georgia, June 8-10, 2000
Reprint requests to: Borut Gersak, MD, PhD, Department of Cardiovascular Surgery, University Medical Center, Zaloska 7, 1000 Ljubljana, Slovenia, Phone/Fax: + 386 61 1334 162, Email: borut.gersak@maat.si
Submitted on: This manuscript was peer reviewed and accepted for presentation at the Third Annual Meeting of the International Society for Minimally Invasive Cardiac Surgery, Atlanta, Georgia, June 8-10, 2000.
REFERENCES
1. Allen BS, Okamoto F, Buckberg GD, Bugyi H, Leaf J. Studies of controlled reperfusion after ischemia. XIII. Reperfusion conditions: critical importance of total ventricular decompression during regional reperfusion. J Thorac Cardiovasc Surg 92:605-10, 1986. :86309542:
2. Brawley RK. Improved exposure of the mitral valve in patients with a small left atria. Ann Thorac Surg 29:179-81, 1980. :80129167:
3. Buckberg GD. Oxygenated cardioplegia: blood is a many splendored thing. Ann Thorac Surg 50:175-81, 1990. :90343490:
4. Cremer J, Steinhoff G, Karck M, et al. Ischemic preconditioning prior to myocardial protection with cold blood cardioplegia in coronary surgery. Eur J Cardiothorac Surg 12:753-8, 1997. :98117351:
5. Djavakhshvili N. Significance of sinusoids for myocardial blood circulation. Technol Health Care 5:171-4, 1997. :97280277:
6. Eke CC, Gundry SR, Fukushima N, Bailey LL. Is there a safe limit to coronary sinus pressure during retrograde cardioplegia? Am Surg 63:417-20, 1997. :97274082:
7. Gersak B, Trobec R, Krisch I, et al. Loss of endothelium-mediated vascular relaxation as a response to various clamping pressures. Eur J Cardiothorac Surg 10:684-9, 1996. :97029167:
8. Gill IS, FitzGibbon GM, Higginson LA, Valji A, Keon WJ. Minimally invasive coronary artery bypass: a series with early qualitative angiographic follow-up. Ann Thorac Surg 64:710-4, 1997. :97452671:
9. Heijmen RH, Borst C, van Dalen R. Temporary luminal arteriotomy seal: II. Coronary artery bypass grafting on the beating heart. Ann Thorac Surg 66:471-6, 1998. :98391203:
10. Kawasuji M, Yasuda T, Tomita S, Sakakibara N, Takemura H, Watanabe Y. Near-infrared monitoring of myocardial oxygenation during intermittent warm blood cardioplegia. Eur J Cardiothorac Surg 12:236-41, 1997. :97434627:
11. Perrault LP, Menasché P, Peynet J, et al. On-pump, beating-heart coronary artery operations in high-risk patients: an acceptable trade-off? Ann Thorac Surg 64:1368-73, 1997. :98047937:
12. Pirc B, Jezernik J, Erzen V, et al. Neoton (phosphocreatine) an additive to cold crystalloid cardioplegic solution. Brit J Anaesth 74:Suppl 2:A86, 1995.
13. Takahashi T, Kadoba K, Taniguchi K, et al. Repair of postinfarction ventricular septal defect on a beating heart. Ann Thorac Surg 61:1816-7, 1996. :96225261:
14. Tasdemir O, Vural KM, Karagoz H, Bayazit K. Coronary artery bypass grafting on the beating heart without the use of extracorporeal circulation: review of 2052 cases. J Thorac Cardiovasc Surg 116:68-73, 1998. :98335620:
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